1. Field of the Invention
The present invention relates to a body-insertable apparatus, such as a capsule endoscope, which is introduced into a subject and is operated by electric power supplied to execute predetermined functions, and a power supplying method therefor.
2. Description of the Related Art
Recently, in the field of endoscopes, there is proposed a swallowable capsule endoscope. The capsule endoscope has imaging and radio communication functions. During a period from a time when the capsule endoscope is swallowed from the mouth into a subject (human body) for the observation (examination) to a time when the endoscope is ordinary excreted from the body, the capsule endoscope peristaltically moves in the body cavity, or inside the internal organs, such as stomach and small intestine, and successively picks up images in the body cavity.
Image data picked up by the capsule endoscope in the body cavity during the movement of the endoscope in the body cavity are successively transmitted by radio communication to an external device and stored in a memory of the external device. The subject is allowed to freely act without constraint while carrying a receiving device having radio communication and memory functions during a period from a time when the subject swallows the capsule endoscope to a time when the endoscope is excreted from the body. After the capsule endoscope is excreted, a doctor or a nurse displays images of internal organs on a display screen according to the image data stored in the memory and diagnoses the subject (for example, Japanese Patent Application Laid-Open No. 2003-210395).
A reed switch, which operates responsive to an externally applied magnetic field, is sometimes used for turning on the power source to supply electric power to function executing units. In general, in use, the extending direction of an existing reed switch must be aligned with the direction of the magnetic field applied.
However, the capsule endoscope is rotationally symmetric in shape with respect to the longitudinal axis direction and no rule is applied to its rotational directions. The fact makes it difficult to align the direction of the magnetic field with the extending direction of the reed switch. For this reason, to operate the reed switch, the directivity must be checked by, for example, rotating a magnet for generating the magnetic field around the reed switch. The on/off operation of the reed switch is troublesome and cumbersome.